The use of monoclonal antibody technology has allowed the identification and partial characterization of human carcinoma- associated antigens as well as differentiation antigens of mammary and colon epithelium. MAbs provide powerful tools for use in the diagnosis and management of human carcinomas. They have been used for screening and diagnostic purposes for the detection of tumor associated antigens in blood serum assays, and for the radiolocalization of primary and metastatic carcinoma lesions in-situ. Using radiolabeled monoclonal immunoglobulins and fragments, a powerful therapy regime is being developed. The overall goal of this project is to molecularly clone and identify the genes that encode the tumor associated antigens TAG-72 and CEA. We have recently initiated studies for the cloning of TAG-72. These studies include: 1) the construction of cDNA libraries from LS174 mRNA in several prokaryotic and eukaryotic expression vectors. 2) the cotransfection of LS174 tumor DNA with plasmids carrying drug selectable markers into mammalian cells. 3) the construction of oligomeric probes to the peptide sequence of TAG-72 for use as hybridization probes. Additional studies have recently been initiated to study the regulation of CEA expression in colon and breast tumor cell lines after interferon induction. Several DNA probes have been developed to use in Northern blot analysis of poly A selected mRNA from these cell lines.